1. Field of the invention
This invention relates to a flush water supply system for controlling the supplying of flush water to a toilet stool, and more particularly to such a system for controlling the flush water supply to the toilet stool by operating an electrically operable valve mounted in a supply pipe.
2. Description of the Related Art
Heretofore, flush systems are widely used in which flush water is temporarily stored in a tank and is then discharged over the bowl of a toilet stool at need. A common problem with the conventional flush systems is that a relatively large space is required for installation of the tank. To this end, a solution has been disclosed in Japanese Patent Publication No. 30092/1980, in which an electrically operable valve is mounted in a supply pipe and is driven under the control of a control unit to supply flush water to the toilet stool directly, i.e. not via any tank.
In this prior system, the supply pipe is branched into two branch pipelines, and a pair of electromagnetic valves is mounted one in each of the branch pipelines for supplying flush water to a bowl of the toilet stool and also to a jet nozzle. As a flush start switch, for example, is operated, the control unit drives the individual electromagnetic valves in a preset order to an opened position for a predetermined period of time to supply flush water to the bowl.
However, this prior system has the following problem especially in controlling the amount of supply of flush water by varying the time duration of opening the individual electromagnetic valves.
The supply pressure of the supply pipe depends on the position of installation of the toilet stool; therefore, with constant time duration used for opening the electromagnetic valves, if the supply pressure is relatively high, the amount of supply of flush water would be excessive so that the sound of flushing is increased to create a splash as well as being undesirable from the viewpoint of saving water. And if the supply pressure is relatively low, the amount of supply of flush water would be insufficient and would cause incomplete flushing of the toilet stool.
It could be considered to provide the control unit with the function of adjusting the time duration of supplying flush water, and to thereby set the time duration of water supply individually depending on the supply pressure at the position of installation of the toilet stool. This hypothetical control unit is complex in structure and additionally has the following problems.
Partly since the supply pressure of the supply pipe would occasionally be different between day and night, and partly since it temporarily varies as another water spigot is turned on, it is difficult to keep the amount of supply of flush water within a predetermined range without being influenced by the fluctuation of the supply pressure